1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to an integrated liquid crystal display device having an organic electroluminescent display (OLED) element as a backlight source.
2. Description of the Related Art
A liquid crystal display (LCD) presents images by controlling the orientation of the liquid crystal molecules which in turn control the transmission of light. LCDs are frequently provided with a backlight module to enhance contrast and display visibility.
Conventionally, in most liquid crystal display devices, the backlight module comprises fluorescent tubes arranged in parallel to a light guide plane, with a back reflector to enhance brightness, and a diffuser layer on the light guide plane to provide more uniform illumination to the liquid crystal device. In portable displays, for example, those used in mobile computers, small diameter cold cathode fluorescent tubes are situated at one end or at opposing ends of a light guide panel which directs light toward the liquid crystal device. Conventional backlight modules with fluorescent lamp sources are, however, thicker and limits scaling development.
Additionally, in conventional liquid crystal display devices, polarizers are adhered to the outside surfaces of the liquid crystal display panel and gaps may remain between the polarizers and the liquid crystal display panel. The gaps allow light leakage, decreasing the light utilization efficiency of the liquid crystal display device.
Among currently used liquid crystal display devices, polarizers and a color filter are typically employed. Polarizers, however, only block about 50% of the light during light polarization and drastically reduce the light utilization efficiency of the liquid crystal display device. That is, the light utilization efficiency decreases to 25% when the liquid crystal display device employs two polarizers. Moreover, color filters only block about 66% of the light, thereby further reducing the light utilization efficiency.
FIG. 1 is a sectional view of a traditional LCD device. As shown in FIG. 1, the traditional LCD device includes a lower substrate 10, an upper substrate 90, and a liquid crystal layer 50 interposed therebetween. The lower substrate 10 can be a glass substrate comprising a thin film transistor (TFT) array. A pixel electrode 20 is formed on the lower substrate 10. A lower alignment film 30 is formed on the pixel electrode 20. A color filter 80 is formed on the interior surface of the upper substrate 90. A common electrode 70 is formed on the color filter 80. An upper alignment film 60 is formed on the common electrode 70. An upper polarizer 40 is disposed (or adhered) on the exterior surface of the upper substrate 90. A lower polarizer 45 is disposed (or adhered) on the exterior surface of the lower substrate 10. A backlight module 95 is disposed below the lower polarizer 45.
The traditional LCD device has poor light utilization efficiency and scaling limitation problems. Thus, a thinner LCD structure with improved light utilization efficiency is called for.